1. Field of the Invention.
This invention relates to the field of absorbent products, especially for use by persons with incontinence. Specifically, the invention is concerned with diapers or underpants type products, as well as absorbent pads and the like, which are highly absorptive due to the inclusion of a super absorbent polymer in an embossed target area.
2. Description of the Prior Art
There has been a great deal of recent development in the field of personal absorbent products ranging from diapers for infants to adult briefs for people with urinary incontinence. One major area of development has been broadly in the field of super absorbent polymers, such as starches, acrylics, modified cellulose, gums and the like. In some respects, the super absorbent polymers are far superior to cellulose fluff and other conventional absorbent media used in personal absorbent products. For example, the polymers, on a weight basis, have an absorption capacity which is far greater than fluff. In addition, super absorbent polymers retain absorbed liquid, even under pressure, far better than fluff which is subject to "squeeze-out" where absorbed liquid is released from fluff when it is subjected to pressure.
There are some drawbacks, however, to super absorbent polymers used as components of personal absorbent products. Generally, super absorbent polymers are inferior to fluff in terms of rate of absorption of liquid. Another drawback of super absorbent polymers is their susceptibility to what is referred to as "gel-blocking" where a layer containing super absorbent polymer is wetted, the polymer absorbs the liquid and the gelled polymer, which has expanded to many times its dry size, blocks additional liquid from passing through the layer. Super absorbent polymers, because they are finely powdered, present manufacturing difficulties in terms of satisfactory incorporation of the powder into absorbent products. One problem with the superabsorbent polymer powder is migration of the powder from its original position within the product, before the product is wetted.
In the field of apparatus for depositing superabsorbent polymer powder, U.S. Pat. Nos. 4,800,102 and 4,927,346, commonly assigned to Nordson Corporation, disclose two approaches to the task of intermittently depositing polymer onto fluff in discreet areas. U.S. Pat. No. 4,800,102 discloses apparatus including an apertured disc which is rotated about a vertical axis and polymer powder is deposited on the disc from which it is scraped so that it falls through the apertures and onto a fluff layer. U.S. Pat. No. 4,927,346 discloses vacuum deposition apparatus for intermittently depositing polymer powder on a fluff substrate.
Super absorbent polymers have been incorporated into absorbent products in a variety of ways. In some cases, super absorbent polymer is sprinkled into a fluff layer or deposited between two fluff layers, as disclosed in U.S. Pat. No. 4,381,782, but these approaches are plagued by problems arising from the migration of the powder from the place it is deposited. Another approach entails the use of tissue with super absorbent polymer powder fixed to it. Such tissue, also known as laminate, has been used in absorbent products alone and in combination with conventional fluff.
Examples of the use of laminate alone are shown in U.S. Pat. No. 4,568,341. This patent discloses a special laminate structure including undulations and small hinge and flap members formed in the laminate. This laminate structure compensates for the relatively slow absorbency rate of the super absorbent polymer in the laminate.
Composite absorbent products including one or more layers of laminate and one or more layers of fluff are disclosed in U.S. Pat. Nos. 3,888,256, 4,333,465, 4,411,660, 4,592,751, 4,622,036, 4,643,726 and 4,699,619.
U.S. Pat. No. 4,055,180 discloses an absorbent article including super absorbent polymer powder disposed in pockets formed in an absorbent pad.
A product distributed under the trademark SLIMLINE comprises a backing sheet, a facing sheet, a layer of laminate adjacent to the facing sheet and a layer of fluff between the laminate and the backing sheet.